Different WoW servers have different populations. The WoW server I play on used to be roughly 50/50 until sometime around the Ulduar patch, when it became something more resembling 80/20 Alliance (because all the guilds that were pushing content were on Alliance side).
I played Alliance for a good while, until sometime between the Lich King patch and the release of Cataclysm. I switched to Horde to play with people I played with in a former guild. It is this guild I've moved to Star Wars with. I've noticed nothing substantial yet regarding the population of Hyperspace Cannon, but have heard from a lot of Alliance players I knew in WoW who are now playing Jedi in Star Wars.
Obviously, experiences vary greatly from player to player. That's part of why I was confused with your first post!